This application claims priority to prior application JP 2002-105954, a disclosure of which is incorporated herein by reference.
The present invention relates to a connector (which may be called a “card connector”) for use in connection of a small-sized card-like object (which will simply be called a “card” hereinafter) such as a SIM (Subscriber Identity Module).
For example, a connector of the type is disclosed in FIGS. 11-16 of Japanese Unexamined Patent Publication No. H08-162199 (JP 8-162199 A). Referring to FIGS. 1 and 2, description will be made of a typical structure of the connector.
The connector illustrated in the figures comprises a plurality of conductive contacts 311, an insulator 321 holding the contacts 311, and a cover 331 for pressing a card 341 towards a principal surface 321a of the insulator 321 to electrically connect the card 341 to the contacts 311. Each of the contacts 311 has a contacting portion 313 protruding on the principal surface 321a of the insulator 321. In the state where the cover 331 is opened as shown in FIG. 1, the card 341 is mounted on the principal surface 321a of the insulator 321. In this event, a plurality of card contacting portions (not shown) of the card 341 are faced to the contacting portions 313 of the contacts 311, respectively. When the cover 331 is pressed and closed as shown in FIG. 2, the card 341 is pressed towards the principal surface 321a of the insulator 321 so that the card contacting portions are brought into press contact with the contacting portions 313.
The insulator 321 has a pair of support shaft portions 325 supporting the cover 331 so that the cover 331 is rotatable in a closing direction I and an opening direction II in which the cover 331 is pressed and closed towards the principal surface 321a of the insulator 321 and in which the cover 331 is separated from the principal surface 321a, respectively. The support shaft portions 325 respectively protrude on a pair of side surfaces 321c of the insulator 321 which are perpendicular to the principal surface 321a. 
The cover 331 has a plate portion 333 to face the principal surface 321a of the insulator 321 when the cover 331 is closed, and a pair of bearing portions 335 facing the side surfaces 321c of the insulator 321, respectively. The bearing portions 335 are perpendicularly bent with respect to the plate portion 333. Each of the bearing portions 335 is provided with a shaft hole 335a engaged with each of the support shaft portions 325.
The plate portion 333 further has a pair of engaging portions 334. Each of the engaging portions 334 is provided with an engaging hole 334a to be engaged with each of a pair of engaging protrusions 328 formed on the side surfaces 321c of the insulator 321.
Supposing that the contacting portions 313 are arranged in two rows, three in each row, estimation is made of operating force required to close the cover 331. It is assumed here that the distance from the center of rotation of the cover 331 to a rotating end (substantially equal to the length of the card) is equal to L and that the distances from the center of rotation to the contacting portions 313 in the two rows are equal to L/3 and 2L/3, respectively. In this event, the relationship given by Equation (1) holds:P×L=L/3×3p+2L/3×3p,  (1)where P represents the operating force required to close the cover 331. From Equation (1), the operating force P required to close the cover 331 by pressing the rotating end of the cover 331 is given by:                                                         P              =                                                (                                                                                    L                        /                        3                                            ×                      3                      ⁢                      p                                        +                                          2                      ⁢                                              L                        /                        3                                            ×                      3                      ⁢                      p                                                        )                                /                L                                                                                        =                              3                ⁢                                  p                  .                                                                                        (        2        )            
The above-mentioned connector utilizes the principle of leverage. However, it is difficult to considerably reduce the operating force P.
The cover 331 is locked only by engagement between the engaging portions 334 and the protruding portions 328 to keep the card 341 in a pressed state. If the engagement is undesiredly released, the cover 331 is easily opened so that the pressed state is no longer kept. Furthermore, the card 341 may unintentionally be dropped off from the connector and damaged.
A similar technique is disclosed in Japanese Unexamined Patent Publication No. H10-144391 (JP 10-144391 A) but has a similar problem.